Optical mapping of neuronal activity during seizures in zebrafish

Mapping neuronal activity during the onset and propagation of epileptic seizures can provide a better understanding of the mechanisms underlying this pathology and improve our approaches to the development of new drugs. Recently, zebrafish has become an important model for studying epilepsy both in basic research and in drug discovery. Here, we employed a transgenic line with pan-neuronal expression of the genetically-encoded calcium indicator GCaMP6s to measure neuronal activity in zebrafish larvae during seizures induced by pentylenetretrazole (PTZ). With this approach, we mapped neuronal activity in different areas of the larval brain, demonstrating the high sensitivity of this method to different levels of alteration, as induced by increasing PTZ concentrations, and the rescuing effect of an anti-epileptic drug. We also present simultaneous measurements of brain and locomotor activity, as well as a high-throughput assay, demonstrating that GCaMP measurements can complement behavioural assays for the detection of subclinical epileptic seizures, thus enabling future investigations on human hypomorphic mutations and more effective drug screening methods. Notably, the methodology described here can be easily applied to the study of many human neuropathologies modelled in zebrafish, allowing a simple and yet detailed investigation of brain activity alterations associated with the pathological phenotype

Equianalgesia, opioid switch and opioid association in different clinical settings: a narrative review

Emergency or postoperative pain often represents an authentic challenge in patients who were already on opioid treatment for chronic pain. Thus. their management requires not only the physician's ability to treat acute pain. but also competence in switching the opioid that lost efficacy. Different aspects should be considered, such as opioids titration, switching, association and equianalgesia.The objective of this paper is to provide a narrative review. which has been elaborated and discussed among clinicians through an iterative process involving development and review of the draft during two web-based meetings and via email. This expert opinion aims to facilitate the correct opioid use through appropriate practices with a focus on pain treatment in emergency and postoperative pain.Equianalgesia tables were reviewed and integrated by clinicians and researchers with expertise in anesthesia, postoperative medicine, intensive care, emergency medicine pharmacology and addiction medicine. Special populations (liver/kidney failure. elder, pediatric, pregnancy/lactation) are discussed in detail along with other critical scenarios, such as: (i) rapid pain worsening in chronic pain (aggravating pain due to disease progression or tolerance development to analgesic therapy): (ii) acute pain on maintenance treatment: and (iii) pain management of complicated patients in emergency care.Extended and updated equianalgesia tables and conversion rates for 17 different opioid formulations (of 9 different molecules) are presented as follows.Opioids remain the class that best suits clinical needs of emergency and post-operative medicine. However, it should be stressed that equianalgesia can be affected by drug-to-drug interactions and pharmacological imprecision. in a complex field where clinical experience may be the main guiding principle

Selective HCN1 block as a strategy to control oxaliplatin-induced neuropathy

Chemotherapy-Induced Peripheral Neuropathy (CIPN) is the most frequent adverse effect of pharmacological cancer treatments. The occurrence of neuropathy prevents the administration of fully-effective drug regimen, affects negatively the quality of life of patients, and may lead to therapy discontinuation. CIPN is currently treated with anticonvulsants, antidepressants, opioids and non-opioid analgesics, all of which are flawed by insufficient anti-hyperalgesic efficacy or addictive potential. Understandably, developing new drugs targeting CIPN-specific pathogenic mechanisms would dramatically improve efficacy and tolerability of anti-neuropathic therapies. Neuropathies are associated to aberrant excitability of DRG neurons due to the alteration in the expression or function of a variety of ion channels. In this regard, Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels are overexpressed in inflammatory and neuropathic pain states, and HCN blockers have been shown to reduce neuronal excitability and to ameliorate painful states in animal models. However, HCN channels are critical in cardiac action potential, and HCN blockers used so far in pre-clinical models do not discriminate between cardiac and non-cardiac HCN isoforms. In this work, we show an HCN current gain of function in DRG neurons from oxaliplatin-treated rats. Biochemically, we observed a downregulation of HCN2 expression and an upregulation of the HCN regulatory beta-subunit MirP1. Finally, we report the efficacy of the selective HCN1 inhibitor MEL57A in reducing hyperalgesia and allodynia in oxaliplatin-treated rats without cardiac effects. In conclusion, this study strengthens the evidence for a disease-specific role of HCN1 in CIPN, and proposes HCN1-selective inhibitors as new-generation pain medications with the desired efficacy and safety profile

Metabotropic glutamate receptor 1 (mGluR1) and 5 (mGluR5) regulate late phases of LTP and LTD in the hippocampal CA1 region in vitro

The group I metabotropic glutamate receptors, mGluR1 and mGluR5, exhibit differences in their regulation of synaptic plasticity, suggesting that these receptors may subserve separate functional roles in information storage. In addition, although effects in vivo are consistently described, conflicting reports of the involvement of mGluRs in hippocampal synaptic plasticity in vitro exist. We therefore addressed the involvement of mGluR1 and mGluR5 in long-term potentiation (LTP) and long-term depression (LTD) in the hippocampal CA1 region of adult male rats in vitro. The mGluR1 antagonist (S)-(+)-α-amino-4-carboxy-2-methylbenzene-acetic acid (LY367385) impaired both induction and late phases of both LTP and LTD, when applied before high-frequency tetanization (HFT; 100 Hz) or low-frequency stimulation (LFS; 1 Hz), respectively. Application after either HFT or LFS had no effect. The mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP), when given before HFT, inhibited both the induction and late phases of LTP. When given after HFT, late LTP was inhibited. MPEP, given prior to LFS, impaired LTD induction, although stable LTD was still expressed. Application after LFS significantly impaired late phases of LTD. Activation of protein synthesis may comprise a key mechanism underlying the group I mGluR contribution to synaptic plasticity. The mGluR5 agonist (R,S)-2-chloro-5-hydroxyphenylglycine (CHPG) converted short-term depression into LTD. Effects were prevented by application of the protein synthesis inhibitor anisomycin, suggesting that protein synthesis is triggered by group I mGluR activation to enable persistency of synaptic plasticity. Taken together, these data support the notion that both mGluR1 and mGluR5 are critically involved in bidirectional synaptic plasticity in the CA1 region and may enable functional differences in information encoding through LTP and LTD